(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Handbook Of Chemical Engineering - I"

POWER GENERATION AND TRANSMISSION
STANDARD  FIRE-TUBE  BOILERS—NATIONAL  ASSOCIATION  OF  TUBULAR BOILER MANUFACTURERS (ABRIDGED)
									OQ	X
	8	w	«>	3H-in. tubes		4-in. tubes		S3*	TJ 03	
	o 8-	a	a>					0} ,4 02	^	•*»
				Q	bo a> .2   08		W)   g			
	£	"*	•»•»		*•**   S3	"o	"-*3   s	O	O	^  o
	1	S Q)	a	03 .0	|   |	*	1   «	i M	1	a
	1	S	o	SJ	3|~	ll	•a i -S T •**	1 1	II	sl
	&	S	H	3   3 55 *»	gBl	1 5	£ -S 8 E-i   a «S	iM	S-2	5-8
100 Ib. working pres-	70	54	16	44	796	36	754	He	a Ke	54 X 54
sure:   double-riveted	90	60	18	54	1,079	44	1,018	KB	K6	60 X 60
longitudinal joints.	110	66	18	66	1,296	54	1,225	1^2	Ke	66 X 60
	150	72	18	86	1,645	70	1,546	^	Yz	72 X 60
125 Ib. working pres-	90	60	18	54	1,079	44	1,018	^	Ke	60 X 60
sure: triple-r i v e t e d	110	66	18	66	1,296	54	1,225	1%2	Ke	66 X 60
longitudinal joints.	150	72	18	86	1,645	70	1,546	Ke	M	72 X 60
	180	78	18	110	2,059	88	1,904	Ji	Ke	78 X 60
150 Ib. working pres-	90	60	18	54	1,079	44	1,018	i^2	H	60 X 60
sure:  quadruple-	110	66	18	66	1,296	54	1,225	1%2	3^	66 X 60
riveted    longitudinal	150	72	18	86	1,645	70	1,546	H	Ke	72 X 60
joints.	180	78	18	110	2,059	88	1,904	»»,	«.	78 X 60
NOTE: The rated horsepower in the above is based on an allowance of 10 to 12 sq. ft. of total heating surface per horsepower. The grate area should be varied to suit the particular coal used.
H in. for shell diameters of 72 in. or more. Thicknesses exceeding %6 in. are uncommon. Efficiencies of double-strap double-riveted butt joints may be as high as 80 per cent. Girth joints may be lap riveted and high efficiency is not necessary. The usual value of the factor of safety is 5.
Heads are made M ia. thicker than shells. The expanded-in tubes help to stiffen them. Additional support is provided by through braces (rods) running from head to head. Unsupported areas above or below the tubes must be further braced. Diagonal stays are preferred because they interfere least with accessibility for internal inspection. Usually five such stays are used at each end, above the tubes, running from head to shell. The allowable stress per square inch (pressure X area supported X length of stay -5- distance from head to attachment to shell) varies from 6,000 to 8,000 Ib. according to material and size. The maximum pitch at the head varies from 5K to 7 in., decreasing as the pressure increases and increasing with the thickness of head plate.
Tubes are 3 in. diameter (rarely less) for hard coal, 3 in. or more for soft coal. Small tubes increase the heating surface and capacity but are hard to keep clean. Lap-welded soft steel is generally used for tubes. Charcoal iron and open-hearth seamless steel are also available. Tubes are seldom over 60 diameters long: long tubes deflect and leak at the ends. They should be kept about 3 in. away from the edge of the tube sheet. Tube pitch may be about one and two-fifths times diameter, decreasing somewhat if the water is exceptionally good. Tube groups are often divided at the middle by a wide vertical gap to increase accessibility for cleaning and to improve water circulation. For similar reasons, the horizontal pitch may be J^ "to 1 in. greater than the vertical pitch. Tubes must not be carried too high in the shell, else steam room will be sacrificed and the boiler may throw moisture. A manhole (not less than 11 by 15 in.) should be provided in one head above the tubes and a han dhole in each head below them. If one of the latter is a manhole, cleaning will be made easier.